Heart disease is the leading cause of death worldwide, accounting for 15 million deaths across the globe in 2015. In many forms of heart disease, decreased cardiac efficiency stems from changes in mitochondrial energy metabolism. Mitochondria are sub-cellular compartments in which metabolites derived from glucose and fatty acids are oxidized to produce high-energy molecules. Increasing fatty acid oxidation in the heart decreases glucose oxidation, and vice versa. Glucose oxidation is a more efficient source of energy, but in certain types of heart disease, such as heart failure, ischemic heart disease, and diabetic cardiomyopathies, fatty acid oxidation predominates in cardiac mitochondria. As a result, the pumping capacity of the heart is reduced.
Existing drugs that redress the balance between glucose oxidation and fatty acid oxidation in cardiac mitochondria have serious shortcomings. Foremost among them is that such drugs address only part of the problem: the reliance on fatty acid oxidation in lieu of glucose oxidation causes a 10% reduction in efficiency in energy production, but patients with heart disease often show a decrease in cardiac efficiency of up to 30%. Consequently, existing approaches to improve cardiac function by altering mitochondrial metabolism are unsatisfactory, and millions of people continue to die from heart disease each year.